Feed roller for printing and like machinery



April 29, 1941. w. GIBSON FEED ROLLER FOR PRINTING AND LIKE MACHINERY Filed Nov. 25, 1938 NVE T William fiib sgr? QM ATTORNEY Patented Apr. 29, 1941 FEED RQLLER FGR PRINTING AN?) LIKE MACHINERY William Gibson, Sidoup, England, assignor to A. Reyrolle & Company Limited, Hcbburn-on- Tyne, England Appiication November 25, 1938, Serial No. 242,324 In Great Britain November 26, 1937 4 Claims.

This invention relates to feed rollers for handling continuous paper webs in printing and like machinery. The invention is of particular importance in connection with the feed rollers used for drawing the printed web from rotary printing presses and will for convenience be described with reference to such rollers, although it will be apparent that it is not limited thereto in its application.

Such a roller is commonly driven through gearing from the press in such a way that its peripheral speed approximates to that at which the web leaves the press, and in order to maintain a suitable tension in the web, the roller is arranged to have a slight excess of peripheral speed and the printed web is held against it by rubber wheels running in the spaces between the fresh print. Thus by varying the pressure on these wheels the friction between the roller and the web, and consequently the tension in I the latter, may be adjusted.

With such arrangements, the surface of the roller becomes worn by friction into grooves under the rubber wheels, and as a result all accuracy of adjustment is lost and the roller has to be renewed or re-surfaced. Moreover, the constant friction between the web and the roller generates static electricity, and where printing speeds are high the static charge in the web causes the latter to "float and renders it generally unmanageable by the cutting and folding machinery.

With the object of avoiding these disadvantages, the present invention comprises driving means for a feed roller including an electrical or other coupling adapted, by continuous slippage, to impose on the roller an accelerative web-tensioning torque insuiiicient to cause slip between the roller and the web.

The arrangement may be such that the webtensioning torque is automatically maintained substantially constant at a predetermined value independently of the speed of the roller, or if preferred it may be automatically varied in a predetermined manner by variations in the roller speed.

The invention may be carried into practice in a large number of alternative ways. For example the coupling referred to may comprise a clutch in the drive to the roller, the slip in the system being confined to this clutch instead of occuring between the roller and the web. Such a clutch might be of the fluid flywheel type or might include means automatically decreasing its degree of engagement if the slip in it decreases unduly, in order to guard against any possibility of the slip being transferred elsewhere.

Preferably, however, there is provided a form of electrical power transmission having the necessary quality, and the following examples and accompanying drawing show how this may be done.

Of the drawing:

Figure 1 is a diagrammatic illustration of a convenient arrangement for driving a single feed roller in accordance with the invention, and

Figure ,2 is a diagram showing how the arrangement of Figure 1 may be modified for driving a plurality of feed rollers.

In the arrangement shown in Figure 1, the armature of a D. C. generator I is geared to and driven by a suitable shaft 2 in the printing press, and is connected in series with that of a D. C. motor 3 geared to the feed roller 4 over which the paper web 5 passes. An upper roller 5 runs free and maintains the web in firm contact with the feed roller 4.

The generator I and motor 3 are provided with separately excited shunt fields I and 8 respectively, which are connected in parallel across an external source 9 of steady voltage, a common regulator It being interposed and a balancing regulator I! being connected in series with one field (in series with field 8 in the example shown).

It will be appreciated that when the web 5 is running through the press, the E. M. F. of generator I and the back E. M. F. of motor 3 are each proportional to web speed, assuming that there is no slip between the web and roller 4. Thus these E. Ffs bear a constant ratio to each other, and this ratio may be adjusted to unity by a suitable choice of gear ratio between,

the motor 3 and roller 4 and/or by adjusting the regulator H. When this balance is e iected, no armature current will flow between generator I and motor 3, and the roller 5 will receive no driving torque from the motor.

A positive web-tensioning torque may now be applied to the roller 4 by injecting an armature cur ent into the system from an external source.

This may be done, as shown, by inserting a small D. C. generator !2 in series with generator and motor 3 and driving it at a constant speed, for example by a motor l3 from the source 3. The generator l2 has a separately excited shunt field M and regulator I5 connected across the source 9, so that by adjusting this regulator the armature current injected into the system, and hence the Web-tensioning torque, may be brought to an adequate value which is at the same time insufficient to cause slip between the Web and the feed roller.

The system as above described will normally supply a Web-tensioning torque which remains constant irrespective of the speed of operation of the press. In cases Where it is desired that such torque shall vary with press speed, the necessary correction may be made manually by means of the regulator l5. Alternatively it may be automatically obtained by arranging for the ratio between the E. M. F. of generator I and the back E. M. F. of motor 3 to be slightly greater (or less) than unity, for example by adjusting the regulator H, so that an out-of-balance armature current component appears which rises (or falls) with increasing press speed and modifies the effect of the generator 12 to the required extent.

This system may readily be modified for drivmore than one of the various Web-handling rollers in a printing press by duplicating the motor 3 and associated parts, as shown in Figure 2. By providing each motor 3 With its own series regulator l6, its armature current may be adjusted with an adequate degree of independence of the other motors.

It will of course be understood that the partic ular embodiments described and illustrated may be modified according to requirements Without departing from the invention. For example, where press machinery is driven by A. C. equipment the invention contemplates using an A. C. generator driven by the press and A. C. roller motors of the squirrel-cage type.

I claim:

1. In a printing press or other Web-handling machinery, a main driving shaft, a Web feed roller, and a driving arrangement for said Web feed roller, said driving arrangement comprising in combination an electrical generator positively driven by said main driving shaft, an electrical motor energized by said generator and positively driving said roller, means for supplying a sub stantially constant additional voltage to said rnotor irrespective of the speed oi the latter and of the generator and means for adjusting, over a range extending substantially to unity, the ratio under Working conditions between the E. M, F. of said generator and the baclr M. F. of said motor.

2. In a printing press or other Web-handling machinery, a main driving a web feed roller, and a driving arrangement for said Web feed roller, said driving arrangement comprising in combination an electrical generator positively driven by said in in driving shaft, an electric motor energized by said generator and positively driving said roller, said generator and motor having separately excited field windings, a common regulator for the field windings of said generator and motor, a balancing regulator for the field winding of the motor to set the speed ratio betwee said generator and motor, and a source of substantially constant additional voltage in cirsuit with said motor.

3. A driving arrangement, as claimed in claim 2, including means for adjusting the value of said constant additional voltage.

l. In a printing press or other Web-handling machinery, a main driving shaft, a plurality of Web feed rollers, and a driving arrangement for said web feed rollers, said driving arrangement, comprising in combination an electrical generator positively driven by said main driving shaft, a plurality of electric motors energized together by said generator and each positively driving one oi said rollers, a source of substantially constant additional voltage in circuit With all said motors, said generator and motors having separately e cited field windings, and means associated with each motor for adjusting its field strength relatively to that of said generator and for adjusting its armature current.

'WILLIAM GIBSON. 

